The US Honda guys get lower quality fuel & the Honda d16 is legendary with vitara pistons, pretty much anyone running boost goes for Vitara pistons rather than forgies.
The common hp w/ pump 91 was around 300-380hp when I last checked on 24psi for safety but now over 450hp atw with over 25psi. I cant find the threads of the d16 dailys running 24psi but a few where running for 4 yrs+ w/ vitara slugs, here`s one thats going close to the hp mentioned but there are heaps & obviously w/ better fuel quality.http://hondaswap.com/forced-induction/vitara-d16-73748/
eg. Vitara slugs record in drag racing 635whp/421tq @ 38psihttp://www.clubcivic.com/board/showthread.php?t=190923
The quality of vitara pistons used are chinese made not japanese cast ones which should be better also vitara pistons are 28.5 or so comp height not over 30mm like A series. Also another thing to consider is the 4 valve notches weaken the vitara pistons unlike the A series with often dont have any like on the E15ET pistons with are also used on low comp A14 and A15 engines where fuel quality is low. Lastly rings on the Vitara are very thin & almost halve A series. Eg. g16b 1.2mm, 1.5mm, 2.5mm versus A15 2mm,2mm,3.5mm (cant remember but A series are much thicker) have to check acl catalogue for accuracy.